1. Field of the Invention
The present invention relates to an information processing apparatus, an information processing method adopted in the apparatus and a presentation medium for presenting the method. More particularly, the present invention relates to an information processing method capable of implementing copy control with a high degree of reliability, an information processing apparatus adopting the method and a presentation medium for presenting the method.
2. Description of the Related Art
FIG. 12 is a diagram showing a typical configuration of an information recording and playback system. As shown in the figure, an IRD (Integrated Recorder/Decoder) 71, digital-signal recording apparatuses 72 and 73 and a digital-signal playback apparatus 74 are connected to each other by IEEE1394 serial buses 75.
In the IRD 71, a receiving circuit 81 receives a satellite broadcast, supplying a transport stream of the received broadcast to a packetizing circuit 82. The packetizing circuit 82 converts the transport stream supplied thereto into isochronous packets (IPs) conforming to IEEE1394 digital interface standards. The IPs are supplied to the digital-signal recording apparatuses 72 and 73.
The digital-signal playback apparatus 74 plays back data recorded on a storage-media unit 111 which corresponds to storage-media units 94 and 103 employed in the digital-signal recording apparatuses 72 and 73 respectively. The reproduced data is then decoded by a recording-format decoder 112. Subsequently, a transport stream output by the recording-format decoder 112 is converted by a packetizing circuit 113 into packets which are then supplied to the digital-signal recording apparatuses 72 and 73 by way of the IEEE1394 serial buses 75.
The digital-signal recording apparatus 72 has a depacketizing circuit 91 for depacketizing data of the isochronous packets supplied thereto through the IEEE1394 serial bus 75 in order to restore the transport stream which is supplied to a recording-format encoder 93 by way of a CCI (Copy Control Information) rewriting circuit 92. The depacketizing circuit 91 also supplies the transport stream to a CCI analyzing circuit 95. The CCI analyzing circuit 95 extracts copy control information (CCI) from the transport stream, analyzes the information and supplies a result of the analysis to a CCI encoder 96.
The CCI encoder 96 encodes (or changes) CCI supplied thereto into new CCI and outputs the new CCI to the CCI rewriting circuit 92. The CCI rewriting circuit 92 rewrites CCI included in the transport stream received from the depacketizing circuit 91 with the new CCI received from the CCI encoder 96, outputting the transport stream to the recording-format encoder 93. The recording-format encoder 93 encodes the transport stream supplied thereto and records the encoded transport stream into the storage media unit 94.
A depacketizing circuit 101 and a recording-format encoder 102 employed in the digital-signal recording apparatus 73 carry out the same processing as the depacketizing circuit 91 and the recording-format encoder 93 respectively employed in the digital-signal recording apparatus 72 on data received from the IEEE1394 serial bus 75, recording a result of the processing into the storage media unit 103. The digital-signal recording apparatus 73 does not have the CCI analyzing circuit 95, the CCI encoder 96 and the CCI rewriting circuit 92 employed in the digital-signal recording apparatus 72. That is to say, the digital-signal recording apparatus 73 functions as a non-cognizant apparatus which is not capable of analyzing CCI recorded in a stream. On the other hand, the digital-signal recording apparatus 72 functions as a cognizant apparatus which is capable of analyzing CCI recorded in a stream.
Next, the operation of the information recording and playback system is explained. An operation to record data received by the IRD 71 is carried out by the digital-signal recording apparatus 73 as follows. When a signal of a predetermined channel is received by the receiving circuit 81 employed in the IRD 71, the transport stream of the signal is supplied to the packetizing circuit 82. The packetizing circuit 82 converts the transport stream supplied thereto into isochronous packets which are supplied to the digital-signal recording apparatus 73 through the IEEE1394 serial bus 75.
In the digital-signal recording apparatus 73, the depacketizing circuit 101 depacketizes the isochronous packets supplied thereto, outputting the transport stream to the recording-format encoder 102. The recording-format encoder 102 encodes the transport stream supplied thereto by adopting a predetermined encoding technique, recording the encoded data into the storage media unit 103.
Data output by the IRD 71 can also be recorded into the digital-signal recording apparatus 72. In this case, the depacketizing circuit 91 depacketizes the isochronous packets supplied thereto through the IEEE1394 serial bus 75, supplying the transport stream to the CCI rewriting circuit 92 and the CCI analyzing circuit 95. The CCI analyzing circuit 95 extracts CCI from the transport stream, analyzes the CCI and supplies a result of the analysis to the CCI encoder 96. In the CCI encoder 96, if the CCI is “copy once”, the CCI is converted into “copy prohibited”. If the CCI is “copy free”, the CCI is not changed. If the CCI is “copy prohibited”, the CCI encoder 96 controls the CCI rewriting circuit 92 to prohibit a recording operation.
The CCI rewriting circuit 92 receives CCI obtained as a result of encoding from the CCI encoder 96. If the CCI received from the CCI encoder 96 is “copy free” or “copy prohibited”, the CCI rewriting circuit 92 rewrites the CCI included in the transport stream received from the depacketizing circuit 91 with the CCI received from the CCI encoder 96, outputting the rewritten transport stream to the recording-format encoder 93. The recording-format encoder 93 encodes the transport stream supplied thereto, recording the encoded data into the storage media unit 94.
As described above, data output by the IRD 71 is recorded. It should be noted that data played back by the digital-signal playback apparatus 74 can also be recorded. In this case, the digital-signal playback apparatus 74 plays back data recorded on the storage-media unit 111. The reproduced data is then decoded by the recording-format decoder 112. Subsequently, a transport stream output by the recording-format decoder 112 is converted by the packetizing circuit 113 into isochronous packets which are then supplied to the digital-signal recording apparatuses 72 and 73 by way the IEEE1394 serial buses 75. Then, a recording operation is carried out in the same way as what is described above.
A transport stream output by the receiving circuit 81 conforms to the MPEG2 systems (ISO/IEC13818-1). In the transport stream, video and audio streams are multiplexed in transport-packet units each having a length of 188 bytes. Assume that the digital-signal recording apparatus 72 is a DVCR (Digital Video Cassette Recorder) for consumer use. In this case, the depacketizing circuit 91 outputs data obtained as a result of addition of 3-byte TSP_extra_header to the head of 187 bytes as shown in FIG. 13. The 187 bytes are the bytes of a transport packet of the transport stream conforming to the MPEG2 systems excluding a byte of the sync_byte at the head of the transport packet. The syntax of TSP_extra_header has a configuration shown in FIG. 14. As shown in the figure, TSP_extra_header includes 21-bit time_stamp_counter which represents a planned arrival time of the first bit of the first byte of a transport packet at an input of a T-STD (Transport Stream System Target Decoder) or a smoothing buffer defined in the ISO/IEC 13818-1 (MPEG2 systems).
In the DVCR, a clock having a frequency of 27 MHz is locked in a PCR (Program_Clock_Reference) included in the transport stream and a clock counter of an arrival of the first byte of a transport packet at the smoothing buffer or the T-STD is added as time_stamp_counter of the transport packet. In a playback operation, a transport packet is output when the clock-counter value of the clock with a frequency of 27 MHz of the DVCR becomes equal to the value of time_stamp_counter of the transport packet.
In the system described above, copy control based on CCI in a cognizant apparatus capable of analyzing CCI can be executed correctly. Since a non-cognizant apparatus is not capable of analyzing CCI, however, there is raised a problem that data is recorded into storage media even if CCI of the data indicates “copy prohibited”. In the case of “copy once” CCI, a copy operation should be allowed only once. It is thus necessary to rewrite the CCI from “copy once” into “copy prohibited” after a copy operation has been carried out once. Since such rewriting is not carried out in a non-cognizant apparatus, however, copy operations may be carried out any number of times.